Fig. 3. Zero infiltration model results for pore water ¹⁸O in three hypothetical soil types: clayey silt, silty sand, and medium sand. Starting from an initial pore water ¹⁸O value similar to winter precipitation at Hanford (–16.5), the model soils were subjected to 20 yr of evaporation and drainage under an atmosphere with h = 40% and ¹⁸O_a = –21. The value of ¹⁸O_MAX that is reached under these atmospheric conditions is shown as a vertical line.